1. Field of the Invention
The present invention relates to a sickleless internal gear pump with cross-sectionally mushroom-shaped sealing elements inserted in the tooth heads, for generation of high pressure.
2. Description of the Related Art
The following prior art has been published:
DE-A-4 104 397 PA1 DE-A-4 140 293 PA1 U.S. Pat. No. 3,429,269 PA1 U.S. Pat. No. 2,866,417.
With the sickleless internal gear pump known from DE-A-4 104 397, only a line seal is created in the area of pressure buildup on the tooth heads, in keeping with the geometric shape of the sealing elements. In case of unfavorable conditions due to tolerance variations, spacing changes or changes of the gear outside diameter, as the case may be, this results in a lack of tightness of the internal gear pump.
DE-A-4 140 293 describes a radially movable sealing element which, without causing excessive manufacturing expense, quite considerably improves the sealing effect in the pressure buildup between opposite tooth heads of the gears, due to the shaping. The contour of the sealing element, for one, and the complementary design of the sealing element and the profile groove in the tooth head, for another, entail several problems, though. Namely, it is unfavorable that, as upon passing dead center the entire system pressure, i.e., the working pressure generated by the pump, acts on the sealing element. For purposes of sealing, a much lower pressure would be sufficient. The high system pressure leads to excessive sealing element wear.
The problem underlying the present invention is to provide an internal gear pump in such a way that the entire system pressure will not be utilized for sealing purposes, and a considerably lower pressure is sufficient for sealing purposes.